Wind farms have just half the useful lifespan which has been claimed, according to new research which found they start to wear out after just 12 years.

A study of almost 3,000 turbines in Britain – the largest of its kind – sheds doubt on manufacturers claims that they generate clean energy for up to 25 years, which is used by the Government to calculate subsidies.

Professor Gordon Hughes, an economist at Edinburgh University and former energy advisor to the World Bank, predicts in the coming decade far more investment will be needed to replace older and ineffective turbines – which is likely to be passed on in higher household electricity bills.

New research: Wind farms have just half the useful lifespan which has been claimed, according to new research which found they start to wear out after just 12 years

He said the performance of the UK’s wind turbines over the past 11 years had ‘deteriorated markedly’ and that ‘the subsidy regime is extremely generous if investment in new wind farms is profitable despite the decline in performance due to age and over time.’

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The research will fuel criticism of wind farms which are already unpopular among many local communities who say they blight the landscape, generate noise and may disrupt wildlife.

But the government which plans to increase the number of turbines from the current 3,873 to 10,000 within the next decade, insists they are essential to fight climate change.

Predictions: Professor Gordon Hughes, an economist at Edinburgh University and former energy advisor to the World Bank

Ministers are currently drawing up plans to compensate local communities affected by them with investment – which have critics have dismissed as bribery.

Prof Hughes’ study of 280 wind farms in Britain and more than 800 in Denmark from 2000 to 2011, found the larger wind farms typical in Britain are less effective than smaller ones.

In Denmark, where wind power has been used for longer, the decline in output was less dramatic, which he said could be down to their smaller size and possibly better maintenance.

For onshore wind, the monthly ‘load factor’ of turbines – a measure of how much electricity they generate as a percentage of how much they could produce if on at full power all the time - dropped from a high of 24 per cent in the first year after construction, to just 11 per cent after 15 years.

For offshore wind –examined only in Denmark where it has been used for longer - it declined even more dramatically from over 40 per cent at the start, to just 15 per cent after ten years.

He believes they become uneconomic after around 12 years. The decline in output was put down to wear and tear of the blades, and more frequent breakdowns for older turbines.

His report for the anti-wind farm charity the Renewable Energy Foundation (KEEP), noted: ‘Onshore wind turbines represent a relatively mature technology, which ought to have achieved a satisfactory level of reliability in operation as plants age. Unfortunately detailed analysis of the relationship between age and performance gives a rather different picture…’

Prof Hughes told the Sunday Telegraph the trend for larger wind turbines in Britain, which reach up to 400feet tall in some areas increased wear and tear.

Future: The research predicts in the coming decade far more investment will be needed to replace older and ineffective turbines - which is likely to be passed on in higher household electricity bills

He added: ‘I strongly believe the bigger turbines are proving more difficult to manage and more likely to interfere with one another.’ He said the data was verified by a statistician at University College London.

It will give ammunition to many Tory MPs who are sceptical about the merits of wind farms and believe the subsidies given to the industry are too high.

More than 100 wrote to the Prime Minister this year saying they were inefficient.

But the Department of Energy and Climate Change say wind produced enough energy to power 2.4million homes in 2011 and they hope this will increase to 7.7million by 2020.

A spokesman said: ‘Our expectations of wind turbine lifetimes are based on rigorous analysis and evidence. Britain’s oldest commercial turbines at Delabole in Cornwall have only recently been replaced after 20 years of operation, and the technology has come on leaps and bounds since that project started generating in 1991.

‘Consumer support for renewable power is based on the actual power generated. That’s why it is in the interest of wind farm operators that they keep their turbines well-maintained and running at optimum capacity.’

The wind farm industry point out that turbines are improving all the time, and say that subsidies are only paid when turbines produce electricity so there is a strong incentive for operators to protect them from wear and tear.